746 Proceedings of the Royal Irish Academy. 



each year, and they last imtil either the middle of Decem- 

 ber (1897 and 1898), or until early in January (1896 and 1897). 

 Professor M'Intosh has made similar observations on the Chse- 

 tognatha of St. Andi'ews Bay. 



Sagitta furcata, Steinhaus (1896). 



3-3 cm. long. In general appearance closely similar to 

 >S^. hexaptera. Eight pairs of hooks. Six anterior and eight 

 posterior pairs of teeth. Paired fins oval. Anterior fins very 

 narrow, placed a short distance in front of the larger posterior 

 ones. Caudal fin bifid. One specimen taken in Valencia 

 Harbour on 28th April, 1895. 



Por a long time I hesitated between describing this example 

 as a new species and regarding it as a variety of Sagitta hexa- 

 ptera. Eecently, however, my friend. Dr. 0. V. Darbishire, 

 drew my attention to a dissertation, " Die Yerbreitung der 

 Chsetognathan im Sudatlantischen und Indischen Ocean," by 

 0. Steinhaus, in which two new forms are described from the 

 rich collection made by the German "Plankton Expedition." 

 Both of them are closely allied to S. hexaptera ; S. planctonis, 

 which has similarly shaped fins, is, however, smaller (2 cm. 

 long), and has well developed "lateral-fields" ; S. furcata, 

 which is over 2 cm. in length, and has very narrow and 

 backwardly-placed anterior fins. The single specimen taken 

 at Valencia agrees so well with the excellent figui'es and 

 description given by Steinhaus, that I have little doubt in 

 regarding it as Sagitta furcata, although future investigation 

 may necessitate a reduction in the increasing number of species 

 resembling S. hexaptera, which at present are regarded as 

 distinct. 



The anterior fins in the Valencia specimen are remarkably 

 narrow, and their anterior ends lie well behind the middle of 

 the body. The posterior ones appear oval in outline, not trian- 

 gular, as in >S'. hexaptera. The caudal fin is distinctly bifid, 

 and produced laterally into a pair of well-developed lobes. The 

 non-muscular margins of the body are as well developed as in 

 S. hexaptera. The hooks, instead of varying between six and 

 seven (as in the latter species), are eight in number, the last 

 four and the fii'st being smaller than the rest. In the same 

 way the teeth agree with those of S. furcata, though they have 

 the terminal five-rayed " star," as in S. hexaptera. The 



